In the prior art, many efforts have been made to improve the stability of short pulse (ie. 100-300 femptosecond range) dye lasers in order to maximize the uniformity of the length, width and power of the output pulses. These efforts have included active stabilization of the length of the resonant cavity. For example, in U.S. Pat. No. 4,815,080 to Chesnoy, a system is disclosed wherein the length of the cavity is actively adjusted based on a measurement of the output wavelength of the laser. More particularly, the output wavelength is detected and an error signal is generated which is used in a feedback loop to control the length of the cavity.
There are many practical problems with the approach described in Chesnoy. For example, this approach does not work well beyond the central tuning frequency of the dye laser. The approach disclosed in Chesnoy is also cavity specific and may not be readily extended to other laser cavities which have different group velocity dispersion.
Another approach for stabilizing a pumped dye laser is disclosed in U.S. Pat. No. 4,314,211, issued Feb. 2, 1982 to Mollenauer. In this device, an error signal is generated by comparing the timing of the output pulses to a reference oscillator. Unfortunately, this approach requires that the length of the cavity of the pump laser must be very stable which is difficult to achieve.
In U.S. Pat. No. 4,727,553, to Fork, an approach is utilized which attempts to balance a number of components within the cavity to minimize the length of the output pulse. In this approach, the group velocity dispersion, self-phase modulation, saturable gain and saturable absorption are all balanced. This approach was used in a colliding pulse mode-locking laser which is pumped by a continuous wave source. This type of laser does not require a length stabilized resonator and therefore, this approach cannot be used alone to obtain short pulses with a synchronously pumped hybridly mode locked linear laser.
Accordingly, it is an object of the subject invention to provide a new and improved ultra fast, stabilized dye laser.
It is another object of the subject invention to provide a laser system with improved stability.